United B38M at Newark on Feb 6th 2024, stuck rudder pedals on landing
Last Update: October 22, 2026 / 15:51:38 GMT/Zulu time
Incident Facts
Date of incident
Feb 6, 2024
Classification
Incident
Airline
United
Flight number
UA-1539
Departure
Nassau, Bahamas
Destination
Newark, United States
Aircraft Registration
N47280
Aircraft Type
Boeing 737-800MAX
ICAO Type Designator
B38M
The aircraft underwent a test flight the following day during which the anomaly was replicated.
On Mar 7th 2024 the NTSB reported:
In a post-incident statement, the captain reported that during the landing rollout, the rudder pedals did not move in response to the “normal” application of foot pressure while attempting to maintain the runway centerline. The pedals remained “stuck” in their neutral position. The captain used the nosewheel steering tiller to keep the airplane near the runway centerline while slowing to a safe taxi speed before exiting the runway onto a high-speed turn-off. While on the high-speed turnoff, the captain asked the first officer to check his rudder pedals and he reported the same problem. The captain reported, that shortly thereafter, the rudder pedals began to operate normally. After parking the aircraft, the flight crew notified UAL maintenance of the flight control malfunction. The airplane was removed from service for maintenance and troubleshooting.
A review of preliminary flight data recorder (FDR) data corroborated the pilot’s statements regarding the malfunction of the rudder system. Data showed that during the landing and subsequent rollout, the rudder surface position remained near its neutral position even though the force inputs to the rudder pedals were observed to be increasing. About 30 seconds after touchdown, a significant pedal force input was observed along with corresponding rudder surface movement. Afterward, the rudder pedals and rudder surface began moving as commanded and continued to function normally for the remainder of the taxi.
On February 9, 2024, UAL conducted a test flight on the event airplane at EWR and was able to duplicate the reported rudder system malfunction identified during the incident. As a result, the test flight profile was discontinued, and the airplane returned to EWR and landed uneventfully.
The NTSB was notified of the flight control issue after the flight test and an incident investigation was started.
The NTSB further reported:
Post-incident troubleshooting and inspection of the rudder control system found no obvious malfunctions with the system or any of its components whose failure would have resulted in the restricted movement observed during flight 1539 and the test flight. As a precaution, the aft rudder input torque tube and associated upper and lower bearings and the rudder rollout guidance servo were removed for further examination by the NTSB systems group.
...
On February 28, 2024, the Systems group met at the Collins Aerospace facility in Cedar Rapids, Iowa to examine and test the SVO-730 rollout guidance servo removed from the incident airplane. The testing was conducted to evaluate the effects that temperature “cold soaking” of the servo might have on the torque required to move the servo’s output crank arm. Testing at room temperature found that the torque to rotate the servo’s output crank arm was within design specifications. The unit was then “cold soaked” for 1 hour and the test was repeated. That testing found that the torque to move the servo’s output crank arm was significantly beyond the specified design limits. Because the servo output crank arm is mechanically connected to the rudder input torque tube, the restricted movement of the servo’s output crank arm would prevent the rudder pedals from moving as observed during flight 1539 and the test flight. Further examination of the SVO-730 rollout guidance servo will be conducted as the investigation continues.
On Sep 27th 2024 the NTSB issued urgent safety recommendations stating that more than 353 rudder actuators would be affected and stated:
Investigators found evidence of moisture in both actuators, which failed testing. Collins Aerospace subsequently determined that a sealed bearing was incorrectly assembled during production of the actuators, leaving the unsealed side more susceptible to moisture that can freeze and limit rudder system movement.
...
The rudder rollout guidance actuator, which is installed in the tail of some B-737NG and 737MAX airplanes, is designed to control the rudder’s movement during category IIIB approach, landing and rollout operations. Although it is not used in non-precision landings, the actuator remains mechanically engaged with the rudder system.
Boeing’s 737 flight manual instructs pilots confronted with a jammed or restricted rudder to “overpower the jammed or restricted system [using] maximum force, including a combined effort of both pilots.” The NTSB expressed concern that this amount of force applied during landing or rollout could result in a large input to the rudder pedals and a sudden, large, and undesired rudder deflection that could unintentionally cause loss of control or departure from a runway.
The NTSB has recommended that Boeing “determine appropriate flight crew responses besides applying maximum pedal force” for such situations in flight or during landing. The NTSB also recommended that Boeing notify flight crews operating 737s with affected actuators that the rudder control system can jam due to moisture that has accumulated inside the actuators and frozen.
Additionally, the NTSB recommended that the FAA determine if actuators with incorrectly assembled bearings should be removed from airplanes, and if so, to direct U.S. operators to do so until replacements are available.
On Sep 30th 2024 the NTSB followed up with a letter to the FAA expressing their concerns that the FAA had not taken action after the first findings and is not appearing to take urgent action now that the NTSB have issued urgent safety recommendations arguing that the aircraft were at risk of loss of control. Two more events with operators outside the USA were known, according to information of the NTSB up to 353 such actuators were produced and delivered, 271 have been installed on aircraft, 16 of them on US Aircraft. The NTSB stated:
Equally concerning is Boeing’s failure to inform United Airlines that the 737 airplanes it had delivered to the airline were equipped with these actuators—and that the actuators were mechanically connected to the rudder control system. We are concerned of the possibility that other airlines are unaware of the presence of these actuators on their 737 airplanes. Consequently, their flight crews may not know what to expect if the rollout guidance actuator fails at low altitude or during landing and rollout, as occurred in this incident. Not making operators fully aware of the installed systems and equipment on the airplanes delivered to them is unacceptable and cannot continue to be tolerated.
On Oct 22nd 2026 the NTSB released their final report and investigation docket concluding the probable cause of the incident was:
Moisture intrusion through the pressure port inlet of the rudder rollout guidance actuator that accumulated and froze during flight at altitude, resulting in jammed rudder pedal movement.
The NTSB analysed:
Postincident troubleshooting by United Airlines, including test flights, reproduced the pedal control anomaly and identified the rudder rollout guidance actuator (RRGA), part of the rudder control system, as the source of this anomaly. Examination of the incident RRGA confirmed evidence of an accumulation of moisture inside the servo. Specifically, staining patterns within the lower gearbox and motor bowl indicated that accumulated water was sufficient to submerge portions of the lower geartrain and associated bearings. At room temperature, the servo’s crank arm rotated freely. However, when the RRGA was exposed to cold temperatures (“cold soaked”) in a climate chamber, the crank arm became difficult to move by hand, and the measured torque exceeded the test requirement. After the unit returned to room temperature, allowing any frozen moisture to melt, the crank arm again rotated freely. Evidence of water intrusion was observed originating at the pressure port inlet and extending across the upper gearbox area.
It is likely that sufficient moisture entered the RRGA gearbox and subsequently froze when the airplane was operated in cold temperatures. As a result, the frozen moisture restricted movement of the internal geartrain, output crank arm, rudder torque tube, and the flight deck rudder pedals.
Aircraft Registration Data
Incident Facts
Date of incident
Feb 6, 2024
Classification
Incident
Airline
United
Flight number
UA-1539
Departure
Nassau, Bahamas
Destination
Newark, United States
Aircraft Registration
N47280
Aircraft Type
Boeing 737-800MAX
ICAO Type Designator
B38M
This article is published under license from Avherald.com. © of text by Avherald.com.
Article source
You can read 2 more free articles without a subscription.
Subscribe now and continue reading without any limits!
Read unlimited articles and receive our daily update briefing. Gain better insights into what is happening in commercial aviation safety.
Send tip
Support AeroInside by sending a small tip amount.
Related articles
Fleet type match
United B738 at Philadelphia on Oct 23rd 2026, engine shut down in flight
A United Boeing 737-800, registration N24202 performing flight UA-1510 from Denver,CO to Philadelphia,PA (USA) with 133 people on board, was on…
Fleet type match
United B763 over Atlantic on Oct 12th 2026, engine shut down in flight
A United Boeing 767-300, registration N644UA performing flight UA-946 from Washington Dulles,DC (USA) to Amsterdam (Netherlands), was enroute at…
Fleet type match
United B772 at Los Angeles on Oct 21st 2026, turbulence injures 4 cabin crew
A United Boeing 777-200, registration N769UA performing flight UA-1157 from Honolulu,HI to Los Angeles,CA (USA) with 190 passengers and 10 crew, had…
Fleet type match
United B764 at Amsterdam on Oct 14th 2026, pressurization issue
A United Boeing 767-400, registration N67052 performing flight UA-71 from Amsterdam (Netherlands) to Newark,NJ (USA), was climbing out of Amsterdam's…
Fleet type match
United B772 at San Francisco on Oct 6th 2026, engine shut down in flight
A United Boeing 777-200, registration N796UA performing flight UA-7 from San Francisco,CA (USA) to Beijing (China), was climbing through FL280 out of…
Newest articles
Fleet type match
Qantas A332 near Denpasar on Oct 22nd 2026, engine shut down in flight
A Qantas Airbus A330-200, registration VH-EBA performing flight QF-37 from Melbourne,VI (Australia) to Singapore (Singapore), was enroute at FL380…
Fleet type match
United B738 at Philadelphia on Oct 23rd 2026, engine shut down in flight
A United Boeing 737-800, registration N24202 performing flight UA-1510 from Denver,CO to Philadelphia,PA (USA) with 133 people on board, was on…
Subscribe today
Are you researching aviation incidents? Get access to AeroInside Insights, unlimited read access and receive the daily newsletter.
Pick your plan and subscribePartner
ELITE Simulation Solutions is a leading global provider of Flight Simulation Training Devices, IFR training software as well as flight controls and related services. Find out more.
SafetyScan Pro provides streamlined access to thousands of aviation accident reports. Tailored for your safety management efforts. Book your demo today
AeroInside Blog
Popular aircraft
Airbus A320Boeing 737-800
Boeing 737-800 MAX
Popular airlines
American AirlinesUnited
Delta
Air Canada
Lufthansa
British Airways